Horizontal convergence means for in-line beam cathode ray tube

ABSTRACT

A horizontal convergence device for use with a three beam inline color mask-type cathode ray tube includes a pair of rotatably adjustable rod-like multi-pole magnetic members producing &#39;&#39;&#39;&#39;x&#39;&#39;&#39;&#39; and &#39;&#39;&#39;&#39;y&#39;&#39;&#39;&#39; components of magnetic fluxes. Each member is a superposed integration of four defined magnetic entities having a plane of symmetry whereat the magnitude of the x component of the fluxes is zero. The members, positioned on either side of the tube neck portion relative to the terminal electrodes of the interiorly oriented electron gun assembly, are individually adjusted to impart a magnitude of fluxes influencing substantially horizontal movement of the outer beams in a manner counter to movement of the center beam, thereby effecting enhanced static convergence of the beams at the plane of the mask.

United States Patent [1 1 Budd [ HORIZONTAL CONVERGENCE MEANS FOR IN-LINE BEAM CATHODE RAY TUBE [75] Inventor: Raymond A. Budd, Seneca Falls,

[73] Assignee: GTE Sylvania Incorporated,

Stamford, Conn.

[22] Filed: June 3, 1974 [21] Appl. No.: 475,811

NI l

l g I Dec. 31, 1974 Primary Examiner-G. Harris Attorney, Agent, or Firm-Norman J. OMalley; Frederick H. Rinn; Cyril A. Krenzer [57] ABSTRACT A horizontal convergence device for use with a three beam in-line color mask-type cathode ray tube includes a pair of rotatably adjustable rod-like multipole magnetic members producing x and y components of magnetic fluxes. Each member is a superposed integration of four defined magnetic entities having a plane of symmetry whereat the magnitude of the x component of the fluxes is zero. The members, positioned on either side of the tube neck portion relative to the terminal electrodes of the interiorly oriented electron gun assembly, are individually adjusted to impart a magnitude of fluxes influencing substantially horizontal movement of the outer beams in a manner counter to movement of the center beam, thereby effecting enhanced static convergence of the beams at the plane of the mask.

6 Claims, 3 Drawing Figures HORIZONTAL CONVERGENCE MEANS FOR IN-LINE BEAM CATHODE RAY TUBE BACKGROUND OF THE INVENTION This invention relates to the convergence of a plurality of electron beams in a cathode ray tube and more particularly to means for effecting horizontal convergence of plural electron beams in an in-line beam color cathode ray tube.

Those cathode ray tubes of in-line beam construction that are conventionally utilized in color television applications, usually have a patterned cathodoluminescent display screen disposed relative to the viewing portion of the envelope face panel. This patterned screen is commonly comprised of several electron responsive color-emitting phosphors disposed as an array of repetitive groupings of areal defined stripes or dots. In plural beam color tubes, the patterned screen is structured in a manner whereby the respective coloremitting screen elements are individually excited when selectively impinged by, for example, three discrete electron beams emanating from a related electron gun assembly during operation of the tube. A grid or mask member, having defined openings therein, is positioned between the patterned screen and electron gun assembly in an orientation near the screen to assure proper impingement of the respective electron beams on the patterned member. To achieve a coordinated screen display it is important for the three electron beams to converge at the plane of the mask for all deflection angles. Even though the electron guns of an in-line assembly are substantially positioned in a common plane, wherein the side oriented guns are sometimes angled to promote beam convergence, the plural beams emanating therefrom are seldom accurately directed due to manufacturing and componental tolerances. Therefore, an adjustable magnetic convergence arrangement is usually positioned on the exterior of the tube envelope, relative to the forward end of an interiorly positioned gun assembly, to provide corrective magnetic convergence influences on the several electron beams formed therein.

One procedure for achieving desired in-line beam convergence commonly utilizes separate vertical and horizontal convergence means which generally affect both static and dynamic converging influences. Such means are usually positioned on the exterior of the tube neck portion in the region of the gun assembly and pro vide compensating influences on the trajectories of the individual beams thereby bringing them into proper relationship for desired convergence at the mask. In effecting static convergence, the several beams are trajectorily adjusted and directed to converge at the center of the mask. As the beams are scanned across the contour of the mask, sequentially covering areas other than the center area, it is necessary to modify angles of the beams by dynamic convergence meansto maintain a continued state of convergence across the plane of the mask. Static convergence of the beams is usually effected by cooperating fields of permanent magnets, while the influences relating to dynamic convergence are conventionally provided by varying electromagnetic fields.

The respective horizontal and vertical, or x and y convergence factors affecting the plural electron beams in an in-line type of color cathode ray tube are usually effected by separate means. Vertical convergence means are often in the form of two substantially E-shaped magnetic cores, one being appropriately placed on either side of the neck portion of the tube in a suitable supporting member. Associated with each of the E-shaped cores are adjustable magnetic means to provide cooperating magnetic fields for influencing movement of the several in-line beams in the y or vertical direction. The degree of movement of the respective beams is dependent upon the position of the poles of the influencing magnetic members, the effective flux density thereof, and position of the beams within the magnetic fields. Horizontal convergence of the plural in-line beams in the x direction often utilizes a pair of substantially U-shaped means, one of which is positioned on either side of the neck portion of the tube relative to the appropriate region of the electron gun assembly encompassed therein. In conjunction with the U-shaped structure, a conventional arrangement for effecting horizontal static convergence of the beams usually employs a rotatably adjustable permanent magnet which is associated with each of the respective core elements of the U-shaped configuration to provide the magnetic fluxes of required densities. On the other hand, to accomplish horizontal dynamic convergence, a horizontal output signal from the television or other dynamic display apparatus, is applied to windings disposed on the legs of each pair of the U-shaped core elements to provide varying electro-magnetic fields.

It has often been the practice in effecting static horizontal convergence to utilize magnetic fields wherein the lines of flux emanating from each of the associated magnets or flux producing members, also effects movement of the center beam in the same direction as that of the adjacently related side beam, such effect being known in the art as beam chasing. While convergence is achieveable by this type of unidirectional influence, there is a tendency for the resultant convergence of the three beams to be moved unduly off center in relation to the axis of the tube. Such excessive off-axis convergence is undesirable since it tends to produce a defocusing of the beams, and may produce errors in associated dynamic convergence, thereby detracting from the display qualities of the tube.

OBJECTS AND SUMMARY OF THE INVENTION It is an object of the invention to reduce and obviate the aforementioned disadvantages evidenced in the prior art. Another object of the invention is to provide a static horizontal convergence device wherein the center beam and a related side beam are magnetically influenced to move in counter directions.

These and other objects and advantages are achieved in one aspect of the invention wherein a horizontal convergence device is comprised of a pair of rotatably adjustable rod-like multi-pole magnetic members effecting x and y components of magnetic fluxes. Each of these flux producing members is a superposed integration of a plurality of four defined magnetic entities, each member being formed to have a plane of symmetry therein whereat the magnitude of the x component of the fluxes is zero. One flux producing member is positioned on either side of the tube neck portion relative to the terminal electrodes of the electron gun assembly interiorly oriented therein, the flux producing member being in a position substantially perpendicular to the plane of the beams. By this orientation, the planes of symmetry of the respective flux producing members are substantially co-existent with the plane of the plural beams emanating from the electron gun structure. The multi-pole magnetic flux producing members are individually adjusted to impart a magnitude of interacting fluxes to influence substantially horizontal movement to each of the outer beams that is in a direction counter to that of the center beam movement thereby effecting improved static convergence of the beams at the plane of the mask.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of a plural in-line beam type of cathode ray tube showing beam convergence means exteriorly oriented thereon;

FIG. 2 is a view taken along the line 2-2 of FIG. 1 illustrating the horizontal convergence means of the in- I vention; and

FIG. 3 is a similarly oriented view illustrating another embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT permeable flux directors for association with the flux generating members, whereupon appropriate windings can be included to effect dynamic convergence in the horizontal direction. Such windings are generally required when the convergence device of the invention is employed with the state of the art relating to a vertical line converging yoke or a uniform field yoke. On the other hand, when quadrapole and self-converging yokes are employed, the convergence device of the invention usually requires no auxiliary windings to achieve dynamic convergence in the horizontal direction, since those yokes are generally designed to effect that correction.

With particular reference to FIG. 1, there is shown a plan view of a plural beam in-line color cathode ray tube 11 having an auxiliary beam deflection system 13 oriented exteriorly thereon. The tube per se has a patterned cathodoluminescent screen 15 of color-emitting phosphor areas disposed on the interior surface of the viewing panel 17, and a longitudinal axis 19 therethrough. An in-line electron gun assembly 21 is positioned within the neck portion 23 of the tube envelope in a manner to direct a plurality of three in-line electron beams 25, 27, and 29 toward the patterned screen 15. Adjacent to the screen and spaced therefrom there is positioned an apertured grid or mask member 31 whereat the plural beams are converged. The exemplary in-line electron gun assembly is partially detailed to delineate three related electron guns 35, 37 and 39 which are aligned in a common plane wherein, in this instance, the axes of the side guns 35 and 39 are angled slightly toward the forward end of the center gun 37. A common convergence electrode assembly 41, comprising a shell of non-magnetic material is terminally integrated on the forward portions of the three electron guns 35, 37 and 39 in a manner that the respective emitted electron beams 25, 27 and 29 are directed therethrough toward the patterned screen 15. While any gun in the assembly 21 may be denoted to excite a particular color-emitting phosphor element of the screen pattern, for purposes of illustration, the sideorlented gun 35 is designated as the green electron gun which emits and directs beam 25 to excite the green phosphor components of the screen pattern. The center gun 37 in the structure is denoted as the red gun from which beam 27 is directed to impinge the red phosphor screen components, while the remaining side gun 39 is denoted as the blue gun producing beam 29 for exciting the blue color-emitting phosphor of the screen pattern.

Shown mounted on the exterior of the tube neck portion 23 adjacent to the gun assembly 21 therein, is a purity device 43 usually comprising two magnetized rings formed to be rotatable about the neck 23 of the tube. Adjustable rotation of the purity rings orients a magnetic field in a manner to exert a force in any desired transverse direction to move all three of the beams transversely of the tube axis 19 and align them with the mask or grid apertures 33 and the respective phosphor patterns of the screen therebeneath.

Exemplarily positioned forward of the purity device 43 is the horizontal convergence means 45 of the invention; and oriented adjacent thereto and forward thereof in the proximity of the yoke is a vertical convergence means 47, such as that described in US. Pat. No. 3,553,523 by Raymond A. Budd and assigned to the assignee of this invention. If desired, the horizontal and vertical convergence means may be positionally interchanged. I

The plural beam deflection system 13 is completed with an associated deflection yoke 49 which is positioned ahead of the convergence means at a location substantially'adjacent the funnel portion 51 of the tube envelope.

Reference is directed to FIGS. 1 and 2 for consideration of the horizontal convergence means of the invention 45 in greater detail. In essence, the essentials of the horizontal convergence device comprise a pair of basic rotatably adjustable rod-like multi-pole magnetic members 53 and 55 producing x and y components of interacting magnetic fluxes. Such members are suitably positioned in an insulative supporting structure 45, the presence of which is shown, but not detailed, in FIG. 1. Each of the flux producing members has a plane of symmetry 59 therein whereat the magnitude of the x component of the fluxes is zero. The members 53 and 55 are positioned one on either side of the neck portion 23 of the tube in an orientation substantially perpendicular to the plane of the beams 61. By such orientation, the planes of symmetry of the flux producing members are substantially coexistent with the plane of the beams emanating from the electron gun assembly 21. Each of the magnetic members is individually adjusted to impart a magnitude of interacting fluxes to influence sub stantially horizontal movement to substantially'each of the outer beams of the array in a direct counter to that ofthe center beam movement thereby effecting static convergence of the beams at the plane of the mask. As shown in FIG. 2, each of the multi-pole magnetic flux producing members 53, 55 is a similar structure being formed as a substantially round rod of a permanent magnetic material having a longitudinal axis 63, 65

therethrough and comprising a plurality of diametrically oriented superjacently related portions. Each of these portions is magnetized in a specific radial manner to provide a superposed integration of a plurality of separate diametrically defined magnetic entities, of which each has a pair of circumferentially oriented north N and south S poles. For instance, as noted in FIG. 2, the N and S poles of the several magnetic entities, comprising each of the flux producing members 53, 55 are aligned in a common plane including the longitudinal axis of the respective magnetic member. The terminal magnetic entities at either end of the respective flux producing members are referenced as M M;, and M M' The two intermediate magnets oriented relative to either side of the common plane of symmetry 59, in each of the flux producing members, are referenced as M M;,, and M M, respectively. In considering the left-oriented rod-like multi-pole member 53 as an example, the terminal magnets M, and M are oriented in polar opposition. Furthermore, the magnets M, and M have similar polar alignments, and magnets M and M have polar alignments that are reverse those of magnets M, and M By this arrangement, the magnetic entities on one side of the plane of symmetry 59 are denoted as having even sub-notations and on the other side odd sub-notations. The terminal magnets M, and M are magnetized to have substantially equal pole flux densities m and m and the intermediate magnets M and M, are magnetized in a similar fashion to have like pole flux densities m and H1 It is evident in FIG. 2 that the magnetic fields of the flux producing members interact to provide substantially symmetrical fields on either side of the plane of the symmetry 59, which, as aforenoted, is substantially coexistent with the common beam plane 61. For purposes of clarity, only representative lines of flux of the adjustable static magnetic fields provided by the flux generating members 53 and 55 are indicated with arrows denoting flux direction. To portray the full extent and magnitude of the respective interacting fluxes would be pictorially confusing. The force exerted upon each beam is perpendicular to both the direction of the influencing lines of flux and the direction of the moving beam; the direction of the force being determined by I the cross-product of the two. Thus, the interacting magnetic fields influence movement of the beams in substantially horizontal directions at the plane of symmetry in varying amounts in accordance with the flux densities of the influencing field.

In describing horizontal convergence influences on the planar array of beams, reference is directed to FIG. 2 wherein the beams are shown as being directed into the plane of the drawing. In accordance with the aforementioned influences, with the viewer facing in the direction of the lines of flux, the directional shift of the beam is to the viewers left. For example, the aforementioned green beam 25 is proximal P" to the muIti-pole flux producing member 53, which is in a maximum flux affecting position, as such, beam 25 is subjected to the strongest magnetic flux and consequently is moved the greatest distance; while the red or center C beam 27 being further from the magnetic member is moved a lesser amount. The blue or distal D beam 29 being furthest from member 53 is influenced a very minimal amount. As later described, beam 29 is primarily influenced by the flux emanating from the multi-pole member 55 positioned adjacent thereto. All beams are subjected to substantially symmetrical magnetic fields. As shown, the interacting magnetic flux fields emanating from the intermediate magnets M and M, are represented by the exemplary line 67 which exerts a substantially horizontal directional force on the proximal beam 27. The sum of the interacting fields of the four magnets M and M and M and M is zero at a point between the proximal P beam 27 and the center C beam 25. As illustrated, the interacting flux fields emanating from the terminal magnets M, and M being represented by the exemplary line 69, is directionally counter to the flux field 67 and consequently influence movement of the center beam 27 in a direction counter to the directional shift of proximal beam 25. Consequently, beam chasing is nonexistent as proximal beam 25 is moved the greatest amount away from the magnetic flux producing member 53 while the center beam 27 is moved a lesser amount toward member 53, and distal beam 29 is moved a very minor amount in the same direction as center beam 27 by a weak portion of the same field 69.

As referenced in FIG. 2, the flux producing member 55 is adjusted in a manner that the interacting flux field 71 emanating from the terminal magnetic entities M',, and M' is exerting little influence on D beam 29. By modifying the adjustment of member 55, the flux field 71 can be increased in intensity to become the controlling influence on the movement of beam 29 and a modifying influence on center beam 27 and to a lesser extent on opposed side beam 25. Thus, by judicious adjustment of both magnetic members 53 and 55 desired movement of the three electron beams 23, 25 and 27 can be effected to expeditiously achieve optimum horizontal convergence without shifting the beams unduly off-axis.

In referring to FIG. 3, there is shown another embodiment of the invention, oriented similar to that shown in FIG. 2, wherein each of the flux producing members 53 and 55' has permeable flux directors 73, and 73', 75 associated with the respective magnets M M and M,, M' to bridge the spacing between the multi-pole members and the neck portion 23 of the tube 11. Such directors in addition to enhancing conduction and positioning of a portion of the interacting magnetic fields emanating from the terminal magnets also provides core means for horizontal dynamic convergence coil windings for those aforementioned instances when such is required by specific yoke and circuitry considerations. The directors are substantially positioned in planes 77 and 79 which are substantially parallel with and substantially equi-distant from the plane 61 of the in-line beams 25, 27 and 29 issuing from the electron gun structure 21 in the tube 11.

As shown in FIG. 3, the flux producing member 53 is rotated substantially from the positioning noted in FIG. 2, thereby re-orienting the poles of the magnetic entities therein with a resultant change in direction of the lines of force of the flux fields. Consequently, the proximal beam 25 and the center beam 27 are moved away from one another; and by way of example, the other muIti-pole member 55' is adjusted to predeterminantly influence the movement of beam 29 adjacent thereto, the direction of influence being counter to that of the center beam 27.

There is also noted in FIG. 3, one type of adjustment means for facily rotating the respective flux producing members 53' and 55, as for example, terminal knobs 81 and 83.

Thus, a horizontal convergence device is provided for use with a three beam in-line color cathode ray tube wherein the center and related side beams are movable in counter directions to expeditiously accomplish static convergence with a minimal amount of displacement of the related beams relative to the axis of the tube.

While there has been shown and described what are at present considered the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention as defined by the appended claims.

What is claimed is:

1. A horizontal convergence device for use with a plural in-line beam color cathode ray tube having a cathodoluminescent screen with an apertured mask spatially related thereto and a multi-beam electron gun assembly oriented in a manner to direct beams to said screen, said device being formed for positioning on the exterior of the neck portion of said tube relative to the terminal electrodes of said electron gun assembly interiorly oriented therein and emitting an array of plural in-line beams in a substantially common plane, said device comprising: a pair of rotatably adjustable rod-like multi-pole magnetic members producing x and y components of magnetic flux, each of said multi-pole members having a plane of symmetry therein whereat the magnitude of the x component of the interacting fluxes is zero, said members being positioned one on either side of said tube neck portion in an orientation substantially perpendicular to the plane of said beams with the planes of symmetry of the respective magnetic members being substantially coexistent with the plane of said beams, each of said magnetic members being individually adjusted to impart a magnitude of interacting fluxes to influence substantially horizontal movement to each of the outer beams of said array in a direction counter to that of center beam movement to effect static convergence of said beams at the plane of said mask.

2. A horizontal convergence device according to claim 1 wherein each of said multi-pole magnetic flux producing members is similar being formed as a substantially round rod of a permanent magnetic material having a longitudinal axis therethrough and comprising a plurality of diametrically oriented superjacently related portions, each of said portions being magnetized in a radial manner to provide a superposed integration of a plurality of separate diametrically defined magnetic entities each having a pair of circumferentially oriented north and south poles, the poles of said magnetic entities being aligned in a common plane including the longitudinal axis of said member, and whereof the specific magnetic entities terminating either end of the integration are aligned in polar opposition.

3. A horizontal convergence device according tov claim 2 wherein each of said magnetic flux producing members is a composite of four magnetic entities comprising eight distinct poles.

4. A horizontal convergence device according to claim 3 wherein the terminal magnetic entities of said flux producing member are referenced as magnets M and M and wherein at least two intermediate magnets M and M are oriented relative to either side of the plane of symmetry of said member, and wherein magnets M and M have similar polar alignments, and wherein magnets M and M have similar polar alignments that are reverse those ofmagnets M and M 5. A horizontal convergence device according to claim 4 wherein the terminal magnets M and M in each of said flux producing members are magnetized to have substantially equal pole flux densities m, and m and wherein said intermediate magnets M and M are magnetized to have equal pole flux densities m and m 6. A horizontal convergence device according to claim 4 wherein each flux producing member has permeable flux directors associated with the respective terminal magnets M and M thereof in a manner to substantially bridge the spacing between said members and the neck portion of said tube, said directors being substantially positioned in planes substantially parallel with and substantially equi-distant from the plane of said in-line beams emanating from the electron gun structure in said tube. 

1. A horizontal convergence device for use with a plural in-line beam color cathode ray tube having a cathodoluminescent screen with an apertured mask spatially related thereto and a multi-beam electron gun assembly oriented in a manner to direct beams to said screen, said device being formed for positioning on the exterior of the neck portion of said tube relative to the terminal electrodes of said electron gun assembly interiorly oriented therein and emitting an array of plural in-line beams in a substantially common plane, said device comprising: a pair of rotatably adjustable rod-like multi-pole magnetic members producing x and y components of magnetic flux, each of said multi-pole members having a plane of symmetry therein whereat the magnitude of the x component of the interacting fluxes is zero, said members being positioned one on either side of said tube neck portion in an orieNtation substantially perpendicular to the plane of said beams with the planes of symmetry of the respective magnetic members being substantially coexistent with the plane of said beams, each of said magnetic members being individually adjusted to impart a magnitude of interacting fluxes to influence substantially horizontal movement to each of the outer beams of said array in a direction counter to that of center beam movement to effect static convergence of said beams at the plane of said mask.
 2. A horizontal convergence device according to claim 1 wherein each of said multi-pole magnetic flux producing members is similar being formed as a substantially round rod of a permanent magnetic material having a longitudinal axis therethrough and comprising a plurality of diametrically oriented superjacently related portions, each of said portions being magnetized in a radial manner to provide a superposed integration of a plurality of separate diametrically defined magnetic entities each having a pair of circumferentially oriented north and south poles, the poles of said magnetic entities being aligned in a common plane including the longitudinal axis of said member, and whereof the specific magnetic entities terminating either end of the integration are aligned in polar opposition.
 3. A horizontal convergence device according to claim 2 wherein each of said magnetic flux producing members is a composite of four magnetic entities comprising eight distinct poles.
 4. A horizontal convergence device according to claim 3 wherein the terminal magnetic entities of said flux producing member are referenced as magnets M1 and M2 and wherein at least two intermediate magnets M3 and M4 are oriented relative to either side of the plane of symmetry of said member, and wherein magnets M1 and M4 have similar polar alignments, and wherein magnets M3 and M2 have similar polar alignments that are reverse those of magnets M1 and M4.
 5. A horizontal convergence device according to claim 4 wherein the terminal magnets M1 and M2 in each of said flux producing members are magnetized to have substantially equal pole flux densities m1 and m2 and wherein said intermediate magnets M3 and M4 are magnetized to have equal pole flux densities m3 and m4.
 6. A horizontal convergence device according to claim 4 wherein each flux producing member has permeable flux directors associated with the respective terminal magnets M1 and M2 thereof in a manner to substantially bridge the spacing between said members and the neck portion of said tube, said directors being substantially positioned in planes substantially parallel with and substantially equi-distant from the plane of said in-line beams emanating from the electron gun structure in said tube. 